The most general method, which is employed when a liquid processing such as, for example, a chemical liquid processing or a rinse processing, is performed on a substrate such as, for example, a semiconductor wafer (hereinafter also referred to as a “wafer”), is to supply a processing liquid to the central portion of the substrate in a state where the substrate is horizontally placed and rotated around a vertical axis (see, e.g., Japanese Patent Laid Open Publication No. 2009-59895). In this case, the processing liquid, supplied to the central portion of the substrate, is diffused by centrifugal force, so that the overall surface of the substrate, including a processing target region in which the liquid processing is performed by the processing liquid, is covered with a liquid film of the processing liquid.
When a region, not covered with the processing liquid, is present on the surface of the substrate during the liquid processing, various problems may occur. For example, in the case of a chemical liquid processing, the processing becomes uneven. Further, when a rinse processing is performed on, for example, a patterned substrate with pure water such as, for example, deionized water (DIW), a processing liquid of a previous process (e.g., a chemical liquid) remains in the pattern, which may cause an insufficient rinse processing.
In order to cover the surface of the substrate with the processing liquid, it is affected by the rotation speed of the substrate and the flow rate of the processing liquid. A higher rotation speed of the substrate enables the liquid film of the processing liquid to easily spread. However, there is a scattering problem of the processing liquid (e.g., scattering of the processing liquid to the outside of a cup). In addition, a higher flow rate of the processing liquid enables the liquid film of the processing liquid to easily spread over the overall surface of the substrate. However, there is a problem of increasing the consumption of the processing liquid. What is requested is to cover the surface of the substrate with the liquid film without increasing the consumption of the processing liquid.